1. Field of the Invention
The invention relates to the field of pressure regulators and in particular to water pressure regulators used in irrigation systems and methods for regulating pressure within such systems.
2. Description of the Prior Arts
In-line water pressure regulators used in irrigation and other applications are well known in the art. An example is shown by Moskow, "Fluid Pressure Regulator," U.S. Pat. No. 3,890,999 (1975) which is an in-line pressure drop regulator with a tubular valve member that is externally adjustable, has a controllable response time, and is balanced so that the pressure effect of the input on a controlled outlet pressure is minimized. The valve has a body with two main parts, an inlet part 10 and an outlet part 12 which are secured together through a lock wire 72 which allows the parts to rotate relative to each other. The valve member 100 shown in the cross sectional view of FIG. 2 is held away from seat 58 by spring 114 with the operating pressure being adjustable by turning knurled edge of collar 120 through access slot 126 compressing the spring to increase the output pressure and expanding the spring to reduce it. Fluid at the output passes through a clearance space between tube 106 and bore 92 to act on piston valve 102 urging the valve closed against the biased force of spring 114. Clearance can be controlled during manufacture to set the operating speed. A tighter clearance provides more damping for the valve. In the diaphragm, the valve member uses an O-ring 112 with a relative large piston 102.
Moskow shows the inlet flow making a right turn in order to flow through the valve instead of having a generally straight flow-through pattern. Furthermore, piston 102 has a fixed effective area upon which the controlling pressure is exerted. Although a small clearance is depicted between outlet port 106 and the body 12 of the valve, it is not clear that this provides the same type of resistance to leakage and hence dampening as the much smaller slip distance. Moskow states at column 3, line 27, that:
"Pressure is able to pass through the clearance space between tube 106 and bore 92. The amount of this clearance determines the speed of response time of the regulator . . . Response sensitivity is adjustable by the amount of clearance between the end of tube 106 and bore 94 as described."
Another example is shown by Rosenberg, "Pressure Regulator," U.S. Pat. No. 4,474,207 (1984) which shows a pressure regulator for irrigation systems that has a low pressure drop, particularly at low input pressures. This feature is the result of the regulator member engaging an inner surface of the housing so as to reduce the effective area of the pressure sensitive area, thereby retaining the regulator in a full open position until the output pressure exceeds a predetermined regulated pressure. Once exceeded, the regulator moves and starts to maintain the predetermined pressure. The underlying embodiment has a housing 2 with a plug 4 holding seat ring 12 as best illustrated in the cross sectional view of FIG. 1. Regulator cylinder 38 is biased up by spring 40 down by the outlet pressure bearing on the outer surface of cylinder 38. At low pressures, cylinder 38 is held against housing 2 so that the surface of cylinder 38 is reduced by the amount at end 42 and full flow is provided with the large opening between lower cylinder end 48 in ring 12. When the pressure exceeds the normal regulating pressure and urges cylinder 38 away from housing 2, then the full surface area of cylinder 38 comes into play and normal pressure regulation takes place.
Rosenberg is thus relevant for showing a spring biased pressure regulator having a similar pressure regulating mechanism as shown in Moskow. However, Rosenberg fails to show a straight flow-through design which would be useful in low pressure applications.
Davis, "Control of Liquid Distribution," U.S. Pat. No. 3,253,608 (1966) shows an in-line axial flow nonrestricted externally adjustable pressure controller having a sleeve valve controlled by a diaphragm. Housing 10 holds a sleeve valve 18 that includes two diaphragms 72 and 74. Air pressure supplied through valve 79 acting as biasing spring on diaphragm 72 to counterbalance the outward pressure that acts on diaphragm 74 in order to set the output pressure. In a no-flow condition, valve sleeve 18 seals against flexible valve seat 82.
Davis is relevant for showing a valve seating in which, when valve seat 18 opens up, the full inner diameter of valve seat 18 is available because of the curved nipple-shape of the seating ports 80. Davis contemplates a substantial turn of flow through channel 60. Davis is also relevant for showing rolling diaphragms for use in a pressure regulating valve.
Rogers, "Axial Flow Pressure Regulator," U.S. Pat. No. 4,561,465 (1985) shows an in-line axial flow, spring biased tubular valve regulator that has damping to prevent hunting. As depicted in FIG. 1, body 10 has a passage 12 with tubular valve 78 biased by spring 74. The output pressure acts on valve 58 because end 60 has a larger diameter than end 64. Therefore, the valve is urged by the output pressure to the right end of figure so that end 64 engages seat 54 and controls the output pressure. To prevent hunting, valve 58 is damped by dashpot. The dashpot includes a chamber 82 formed in the body 10 by cylindrical surface 84 and a valve mounted snap ring 86 mounted adjacent the valve end 64 which radially extends into chamber 82 whereby small clearance is provided between the periphery of ring 86 and surface 84. See specifically the cross sectional view of FIG. 2. This clearance defines a damping orifice, establishing communication between chamber 84 and the internal fluid pressure to dampen the valve movement to produce a smooth valve operation during pressure regulation. See this description beginning at column 4, line 4 through line 17.
While Rogers is relevant for showing fluidic friction used as a damping mechanism to prevent hunting in a flow-through valve, the mechanism by which the fluidic resistance is created in the "dashpot chamber" is structurally distinguishable from a small clearance channel. Although the two mechanisms necessarily use the same physical law, they are different means for using fluidic resistance in pressure regulation. Rogers is further distinguished in that the fluidic resistance is provided as a direct retarding force on the motion of the regulating sleeve valve.
Healy et al., "Pressure Regulator," U.S. Pat. No. 4,543,985 (1985) shows an irrigation sprinkler pressure regulator with an in-line axial construction, having a diaphragm supported, spring biased throttling stem. Pressure regulator 10 in FIG. 1 has an upper casing 11, lower casing 12, with passages 15 and 16 containing throttling stem 20 which is slidably mounted and biased away from seat 32 by spring 21 which rides on an adjusting washer 22. Attached to the throttling stem 20 is an annular diaphragm 27. Hunting is eliminated by pressure controller 41 which is closely fitted to allow a small flow through space 46 to chamber 47. A small flow of the output pressure fluid applies pressure against the top surface 35 of stem 20 and ring 30, thereby damping oscillations. See the description beginning at column 3, line 32 through line 63.
Healy is thus relevant for showing a fluidic resistance passage 46 which is used to apply a pressure against a rolling diaphragm 27 to dampen the movement of a pressure regulating sleeve in a flow-through valve system.
Therefore, what is needed is a water pressure regulator for use in irrigation systems which provides for a straight through high volume flow through the regulator, with quiet operation without chatter or oscillation which is characteristic of the in-line pressure regulators described above. Further, what is needed is a design which is reliable and rugged should be inexpensively manufactured without requiring complex machining, moldings or castings.